[Python-Dev] Is Lib/test/crashers/recursive_call.py really a crasher?

Michael Hudson mwh at python.net
Tue Jun 27 19:19:45 CEST 2006

"Brett Cannon" <brett at python.org> writes:

> If you look at that crasher, you will notice that recursion depth is set
> to 1 << 30 before any code is run.  If you remove that setting high
> setting and go with the default then the test doesn't crash and raises the
> appropriate RuntimeError.
> Setting the recursion depth to such a high number will crash the
> interpreter even when the proper recursion checks are in place.  This
> doesn't seem like a legit crasher to me if it requires an insane recursion
> depth that would crash almost any C program that had recursion in it.
> Anyone have any objections if I call foul on the test and remove it
> without any changes to Python?

Yes, it's still a way to crash Python :-) (in fact, a problem vaguely
like this that made a complete test run segfault on 64-bit platforms
was fixed in PyPy recently).

More seriously, the recursion limit approach is IMHO something of a
hack, as the amount of bytes of C stack in between increments is
rather variable (try seeing how high you have to set the recursion
limit to when the recursion invovles list.sort() compared to when it
doesn't).  I don't have a fantastic idea for fixing this, but I quite
like having some kind of reminder of it.


  ZAPHOD:  Who are you?
  ROOSTA:  A friend.
  ZAPHOD:  Oh yeah? Anyone's friend in particular, or just generally 
           well-disposed to people?               -- HHGttG, Episode 7

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